Liquid crystal display (LCD) devices use the optical anisotropy and polarization properties of liquid crystal molecules of a liquid crystal layer to produce an image. The liquid crystal molecules have long and thin shapes, and because of the optical anisotropy property, the polarization of light varies with the alignment direction of the liquid crystal molecules. The alignment direction of the liquid crystal molecules can be controlled by varying the intensity of an electric field applied to the liquid crystal layer. Accordingly, a LCD device includes two substrates spaced apart and facing each other and a liquid crystal layer interposed between the two substrates. Each of the two substrates includes an electrode on a surface facing the other of the two substrates. A voltage is applied to each electrode to induce an electric field between the electrodes and the alignment of the liquid crystal molecules as well as the transmittance of light through the liquid crystal layer is controlled by varying the intensity of the electric field.
Because an LCD device does not include an emissive element, an additional light source is required to view images on the liquid crystal display panel. Accordingly, a backlight unit having a light source is disposed under the liquid crystal display panel. The backlight unit for an LCD device may be classified as either a side light type or a direct type according to the position of the light source relative to the liquid crystal display panel. In a side light type backlight unit, light emitted from at least one side portion of the liquid crystal display panel is redirected by a light guide plate (LGP) to enter the liquid crystal display panel. In a direct type backlight unit, a plurality of light sources is disposed at a rear surface of the liquid crystal display panel so that light from the plurality of light sources directly enters the liquid crystal display panel.
A side light type backlight unit has an advantage in fabrication process to a direct type backlight unit. A cold cathode fluorescent lamp (CCFL), an external electrode fluorescent lamp (EEFL) and a light emitting diode (LED) have been used as a light source of a backlight unit for an LCD device. The liquid crystal display panel and the backlight unit are integrated as a liquid crystal display module using various mechanical elements for protection from external impact and prevention of light leakage.
FIG. 1 is a cross-sectional view showing a liquid crystal display module including a side type backlight unit according to the related art. In FIG. 1, a liquid crystal display module includes a liquid crystal display panel 10, a backlight unit 20, a main frame 30, a top frame 40 and a bottom frame 50. The liquid crystal display panel 10 includes first and second substrates 6 and 4 facing each other and a liquid crystal layer (not shown) between the first and second substrates 6 and 4. Although not shown in FIG. 1, a thin film transistor as a switching element is formed on the first substrate 6, and a color filter layer is formed on the second substrate 4. The liquid crystal display panel displays images according to ON/OFF operation of the thin film transistor. In addition, a gate driving unit and a data driving unit are formed at sides of the liquid crystal display panel 10 as a tape carrier package (TCP) type. The gate driving unit and a data driving unit supply a gate signal and a data signal, respectively, to the liquid crystal display panel. To obtain a space for bonding the gate driving unit and the data driving unit, the first substrate 6 has a larger size than the second substrate 4 such that a first side portion “a” of the first substrate 6 is exposed and an opposite second side portion “b” is covered with the second substrate 4.
The backlight unit 20 that supplies light to the liquid crystal panel 10 is disposed under the liquid crystal display panel 10. The backlight unit 20 includes a fluorescent lamp (not shown) as a light source, a light guide plate 24, a reflecting sheet 26 and a plurality of optical sheets 22. The light guide plate 24 is disposed to face the fluorescent lamp. In addition, the reflecting sheet 26 is disposed under the fluorescent lamp and the light guide plate 24 and the plurality optical sheets 22 are sequentially disposed over the fluorescent lamp and the light guide plate 24.
The main frame 30 has a rectangular ring shape and is formed through a metal press. A plurality of first panel guides 32 and a plurality of second panel guides 34 upwardly protrude to support the liquid crystal display panel 10. As a result, movement of the liquid crystal display panel 10 is prevented.
The top frame 40 covers upper edge portions of the liquid crystal display panel 10 and outer side surfaces of the main frame 30 to protect and support sides of the liquid crystal display panel 10 and the main frame 30.
The bottom frame 50 covers a rear surface of the reflecting sheet 26 and inner side surfaces of the main frame 30. The bottom frame 50 is combined with the main frame 30 and the top frame 40 using a connecting means (not shown) to form the liquid crystal display module.
The above-mentioned structure is applied to a medium-sized model of an LCD device. To support the liquid crystal display panel 10 having a relatively heavy weight, the main frame 30, the plurality of first panel guides 32 and the plurality of second panel guides 34 are formed of a metallic material.
An LCD device may have one of a twisted nematic (TN) mode and an in-plane switching (IPS) mode. When the LCD device has an IPS mode, a transparent conductive layer 5 having indium-tin-oxide (ITO) is formed between the first and second substrates 6 and 4. Since the transparent conductive layer 5 is disposed at edge portions of the first and second substrates 6 and 4, the transparent conductive layer 5 is exposed to the exterior of the liquid crystal display panel 10. The exposed transparent conductive layer 5 may be connected to the second panel guide 34 to cause an electric shortage. Accordingly, the second panel guide 34 at the second side portion “b” is bent under the first substrate 6 to prevent the electric shortage between the second panel guide 34 and the exposed transparent conductive layer 5, while the first panel guide 32 at the first side portion “a” having the gate driving unit and the data driving unit upwardly protrudes to a top surface of the second substrate 4. As a result, the second panel guide 34 supports the first substrate 6.
FIG. 2 is a perspective view showing a main frame of a liquid crystal display module according to the related art. In FIG. 2, first and second panel guides 32 and 34 upwardly protrude from a main frame 30 combining with a bottom frame 50 (of FIG. 1). The second panel guide 34 has at least one embossed portion. Since the first panel guide 32 straightly extends and the second panel guide 34 is bent, the first panel guide 32 is higher than the second panel guide 34. Accordingly, although the first panel guide 32 supports a side surface of a liquid crystal display panel 10 (of FIG. 1), the second panel guide 34 does not support the side surface of the liquid crystal display panel 10 (of FIG. 1). As a result, the liquid crystal display panel 10 (of FIG. 1) may be detached by impact or movement during conveyance or transference to be broken.
Referring again to FIG. 1, the liquid crystal display panel 10 is attached to the main frame 30 using a double-sided adhesive tape 38 to prevent the above-mentioned detachment. However, since an attachment step using the double-sided adhesive tape and an alignment step between the liquid crystal display panel 10 and the main frame 30 are added to a fabrication process for the liquid crystal display module, the fabrication process for the liquid crystal display module is complicated. In addition, production cost increases due to the double-sided adhesive tape.